Road vehicle lighting systems

ABSTRACT

A road vehicle lighting system has first and second dipped beam headlamps, one main beam headlamp and a projector receiver unit which replaces the second main beam headlamp. The unit projects a divergent beam of light, and cuts off sufficient of that beam to prevent dazzling an oncoming driver. The normal dip switch is employed but is arranged to energize the projector-receiver unit in both positions of the dip switch, and when the dip switch is in its second position the minimum strength of the signal required by the receiver to operate the projector receiver unit is increased.

United States Patent 1 Hicks I [54] ROAD VEHICLE LIGHTING SYSTEMS [76]Inventor: Harris Vernon Hicks, 61 Ferndale I Road, Lichfield, England 22Filed: Nov. 15, 1971 [21] Appl. No.: 198,534

[30] Foreign Application Priority Data Nov. 20, 1970 Great Britain..55,209/70 [52] [1.8.01 ..315/83 [51] Int. Cl. ..B60q 1/14 [58] Fieldof Search ..315/82, 83

[56] References Cited UNITED STATES PATENTS 2,965,798 12/1960 Cade..315/83 1 Emmet 1' May 1, 1973 Primary Examiner-Roy Lake AssistantExaminer-James B. Mullins AttorneyHolman & Stern [57] ABSTRACT A roadvehicle lighting system has first and second dipped beam headlamps, onemain beam headlamp and a projector receiver unit which replaces thesecond main beam headlamp. The unit projects a divergent beam of light,and cuts off sufficient of that beam to prevent dazzling an oncomingdriver. The normal dip switch is employed but is arranged to energizethe projector-receiver unit in both positions of the dip switch, andwhen the dip switch is in its second position the minimum strength ofthe signal required by the receiver to operate the projector receiverunit is increased.

2 Claims, 4 Drawing Figures PATENTEU 1 5 sum 1 BF 2 PATENTED 119733.731.141

SHEET 2 [1F 2 ROAD VEHllCLE LIGHTING SYSTEMS This invention relates toroad vehicle lighting systems.

The term projector-receiver unit" is used herein to denote a unitincluding a light projector for projecting forwardly a well-defined,divergent beam of light of generally rectangular cross-section, a lightreceiver for receiving light from a light source in front of the unit,and means responsive to light received by the receiver for cutting offsufficient of the projected beam, from one side of the beam, to ensurethat the beam does not fall on said light source.

A road vehicle lighting system according to the invention comprises incombination first and second dipped beam headlamps, a main beamheadlamp, a projector-receiver unit, a dip switch having a firstposition in which it energises the dipped beam headlamps, and a secondposition in which it energizes the main I beam headlamp, means wherebythe projector-receiver unit is energized in both positions of the dipswitch, and means operable when the dip switch is in its second positionfor increasing the minimum strength of the signal required by thereceiver to operate the projectorreceiver unit.

An example of the invention is illustrated in the accompanying drawings,in which FIGS. 1 and 2 are optical diagrams respectively of theprojector and receiver of a projector-receiver unit,

FIG. 3 is a diagrammatic representation of part of the control apparatusof the projector-receiver unit, and

FIG. 4 is a circuit diagram.

Referring to FIGS. 1 to 3, the projector-receiver unit includes a casinghousing a light projector 11 and a light receiver 12. The projector 11includes a high intensity bulb, and an elipsoidal mirror 13. Thefilament 14 of the bulb is positioned at one focus of the mirror 13, andthe bulb is so positioned that the other focus of the mirror 13 occursin an aperture 16 of a mask 15. Positioned on the side of the maskremote from the bulb is a piano-convex lens 17 the spacing between thelens 17 and the mask 15 being equal to the focal length of the lens 17.The aperture 16 is rectangular, and so a well defined image of theaperture 16 is projected forwardly to constitute a divergent beam oflight of accurately rectangular cross section. Thus when the unit ispositioned on the front of a road vehicle, then the beam of lightilluminates the road in front of the vehicle.

The receiver 12 includes a piano-convex lens 18 which receives lightfromin front of the receiver, and which produces an image in a rectangularaperture 19 in the mask 15. Light passing through the aperture 19 fallson a condensor lens system 21 which directs the light onto thesensitised surface of a photo cell 22. The arrangement is such that animage of the lens 18 falls on and almost fully covers the sensitizedsurface of the photo cell 22. In this way, the image ofthe lnes 18 fallscentrally on the photo cell 22 irrespective of the position of the imagein the aperture 19.:lf the image falls outside the aperture 22, no lightfalls on the cell.

Movable across the apertures 16, 19 respectively are a pair of shutters23, 24 which are interconnected so as to move simultaneously. inpractice, the shutters 23, 24 are integral with one another. Thesh'utters 23, 24 are carried by a spool 25 which also carries a winding'26. Extending through the spool 25'is one inclined limb 28 of arectangular soft iron frame 27. The limb 29 of the frame 27 opposite thelimb 28 has secured thereto a ferrite magnet 31, the magnet 31 beinghoused between the limbs 28, 29 and the width of the magnet 31 beingsubstantially equal to the length of the limb 29. The north pole of themagnet 31 is in contact with the limb 29 and since the frame 27 is aclosed circuit then the whole of the frame 27 is of north polarity withrespect to the south pole of the magnet 31. The south pole of the magnet31 is spaced from the limb 28 of the frame 27 by an air gap, and so partof the magnetic field of the frame 27 and magnet 31 extends between thelimb 28 and the south pole of the magnet 31 at right angles to the limb28. The winding 26 is wound around the spool 25, and so the limb 28passes through the winding.

Electrical connections are made to the winding 26 by way of fine copperpig-tails and the spool 25 can slide along the limb 28. The spool 25,and consequently the shutters 23, 24 is urged by gravity towards thelower end of the limb 28, that is to say to a position wherein theapertures 16, 19 are covered.

In use when the unit is switched on, the winding 26 is energised to movethe spool 'up the limb 28 and so completely uncover the apertures. Whenlight falls on the photo cell 22, the photo cell 22 produces an outputwhich controls current flow in the winding 26, so that the spool 25moves longitudinally down the limb 28 of the frame 27, thereby movingthe shutters 23, 24 in a direction to progressively cover theirrespective apertures 16, 19. The shutters 23, 24 continue to move, untilthe leading edge of the shutter 24 covers that portion of the aperture19 in which the image of the remote light source (for example theheadlamp of an oncoming vehicle) is falling. When this position isreached the photo cell 22 ceases to produce an output, and the shutters23, 24 start to return to their original positions until that portion ofthe aperture 19 into which the image of the remote source falls is againuncovered, whereupon the photo cell 22 again produces an output. Thusthe spool 25 and the shutters 23, 24

will hunt about a position wherein the leading edge of the shutter 24masks the image of the lens 18 falling in the aperture 19. The amplifierof the unit is so designed as toprovide some measure of damping, and ifrequired mechanical damping can also be provided. While the shutter 24is masking part of the aperture 19, the shutter 23 will of course bemasking part of the aperture 16, and since the width of the projectedbeam of light is dependent upon the width of the apertures 16, then theposition of the shutter 23 relative to the aperture 16 will determinethe width of the projected beam. Thus as the shutter 23 moves across theaperture 16 the projected beam will be progressively cut off from oneside of the beam. The correlation between the projector 11 and thereceiver 12 is such that sufficient of the projected beam is cut off toensure that the projected beam does not fall on the light source seen bythe receiver. in the case where the light source seen by the receiver isthe headlights of an oncoming vehicle, then the projected beam will becut 011' sufficiently to prevent the beam falling on the driver of theoncoming vehicle, thereby minimizing the risk that the driver of theoncoming vehicle will be dazzled. When the unit is tumed off, the spool25 moves under gravity to the lower end of the limb 28 so that theapertures are closed, and saturation of the photocell 22 by daylight isprevented.

it will be appreciated that the shutters 23, 24 can be so arranged thatthe projected beam is cut off from either side thereof, that is to saythe projected beam can be cut off from its left side, in one unit, whilein a second unit the arrangement can be such that the beam is cut offfrom its right side.

The projector-receiver unit is employed in a four headlamp systemcomprising a pair of dipped beam headlamps, a main beam headlamp and theprojectorreceiver unit. Referring to the circuit diagram shown in FIG.4, the vehicle battery 41 has its negative terminal connected to anearth supply line 42, and its positive terminal connected through a mainlighting switch 43 to the movable contact of a dip switch 44 having apair of fixed contacts 45, 46. The contact 46 is connected to the line42 through the dipped beam headlamps 47, 48 in parallel, and the contact45 is connected to the line 42 through the main beam headlamp 49. Thejunction of the switch 43 and contact 44 is connected to a supply line51, and the filament 14 of the projectorreceiver unit is connectedbetween the line 51 and the line 42. Also connected between the lines51, 42 in series are a resistor 52, the photo cell 22 and the a resistor53, the resistor 52 being bridged by a thermistor 54 which compensatesfor temperature variations The junction of the photo cell 22 andresistor 53 is connected to the base of an n-p-n transistor 55, thecollector of which is connected to the line 51 and the emitter of whichis connected to the line 42 through a resistor 56, also connectedbetween lines 51, 42 are a pair of resistors 57, 58 in series, thejunction of the resistors 57 and 58 being connected to the emitter ofthe transistor 55 through the winding 26, and further being connectedthrough a resistor 59 to the contact 45.

When the main lighting switch 43 is closed, then assuming that thecontact 44 engages the contact 46, the dipped beam headlamps 47 and 48are energized, and the line 51 is also energized, so that theprojectorreceiver unit is energized. At this stage current can flow fromthe line 51 through the resistors 57 and 59 and the main beam headlamp49 in series to the line 42, but this current flow is insufficient toenergize the headlamp 49. The bridge network 55, 56, 57, 58 controlscurrent flow through the winding 26 in accordance with the conduction ofthe transistor 55, which in turn is controlled by the photo cell 22, andthe projector-receiver unit acts as previously described to preventdazzling the driver of an oncoming vehicle. The various resistancevalues are chosen so that the projector-receiver unit operates to avoiddazzling the driver of the oncoming vehicle.

When the contact 44 is moved into engagement with the contact 45, thedipped beam headlamps 57 and 48 are extinguished, but the main beamheadlamp 49 is energized. The line 51 is still energized of course, andso the projector-receiver unit is still in operation. However, currentflowing from the contact 45 through the headlamp 49 alters the currentflow through the resistor 59, with the effect that the minimum strengthof the signal required to operate the shutters is increased, and in oneparticular example is doubled. The reason for this is that it is foundthat if the projector-receiver unit is used in a system as describedwith a main beam headlamp, then on bends in the road, reflections causedby the main beam headlamp can cause the shutters 23 and 24 to partlyclose, even though there is no vehicle approaching. Clearly this problemcould be solved by arranging that the projector-receiver unit has itsshutters fixed when the main beam position is selected, so that the unitmerely acts as a main beam headlamp, it being appreciated that when themain beam position is selected, there is no necessity for the shuttersto be moved since there should not be any oncoming traffic. However, ifthe shutters are fixed in these circumstances, the photo cell 14 canbecome saturated by extremely bright illumination, and is then slow torespond when the dipped beam position is selected again. By altering thesensitivity of the projector-receiver unit as described, it is foundthat the shutters will not normally close during main beam operation, sothat in effect a second main beam headlamp is provided. However, ifbright illumination is encountered, then the shutters will close toprevent saturation of the photo cell 22.

I claim:

1. A road vehicle lighting system comprising in combination first andsecond dipped beam headlamps, a main beam headlamp, a dip switch havinga first position in which it energizes the dipped beam headlamps, and asecond position in which it energizes the main beam headlamp, a lightprojector for projecting forwardly a well defined, divergent beam oflight of generally rectangular cross-section, circuit means couplingsaid light projector to said dip switch whereby said light projector isenergized in both positions of the dip switch, a light receiver forreceiving light from a light source in front of the road vehicle, awinding which when energized movesa pair of shutters, one of theshutters serving to cut off said divergent beam of light progressively,and the other of said shutters serving progressively to block light fromsaid light source in frontof the road vehicle from entering said lightreceiver, said light receiver incorporating a photo-cell on which lightfrom said light source falls under the control of said other shutter, abridge network having an output coupled to said winding, said photo-cellserving to determine the resistance of one limb of said bridge networkwhereby to determine the position of said shutters, so that said oneshutter cuts off sufficient of the projected beam to ensure that saidbeam does not fall on said light source, the system further includingcircuit means which is energized under the control of said dip switch atthe same time as said main beam headlamp for increasing the minimumstrength of the signal which must fall on said photo-cell to energizethe winding and thereby move said shutters, whereby said receiver isless sensitive to oncoming light when the dip switch is in its secondposition than when the dip switch is in its first position.

2. A system as claimed in claim 1 in which the circuit means operable atthe same time as the main beam headlamp is energized comprises a circuitconnection across one element of the bridge network, said circuitconnection including the main beam headlamp, so that when the main beamheadlamp is illuminated, the setting of the bridge network is altered.

t I? 4 t i

1. A road vehicle lighting system comprising in combination first andsecond dipped beam headlamps, a main beam headlamp, a dip switch havinga first position in which it energizes the dipped beam headlamps, and asecond position in which it energizes the main beam headlamp, a lightprojector for projecting forwardly a well defined, divergent beam oflight of generally rectangular cross-section, circuit means couplingsaid light projector to said dip switch whereby said light projector isenergized in both positions of the dip switch, a light receiver forreceiving light from a light source in front of the road vehicle, awinding which when energized movesa pair of shutters, one of theshutters serving to cut off said divergent beam of light progressively,and the other of said shutters serving progressively to block light fromsaid light source in front of the road vehicle from entering said lightreceiver, said light receiver incorporating a photo-cell on which lightfrom said light source falls under the control of said other shutter, abridge network having an output coupled to said winding, said photo-cellserving to determine the resistance of one limb of said bridge networkwhereby to determine the position of said shutters, so that said oneshutter cuts off sufficient of the projected beam to ensure that saidbeam does not fall on said light source, the system further includingcircuit means which is energized under the control of said dip switch atthe same time as said main beam headlamp for increasing the minimumstrength of the signal which must fall on said photo-cell to energizethe winding and thereby move said shutters, whereby said receiver isless sensitive to oncoming light when the dip switch is in its secondposition than when the dip switch is in its first position.
 2. A systemas claimed in claim 1 in which the circuit means operable at the sametime as the main beam headlamp is energized comprises a circuitconnection across one element of the bridge network, said circuitconnection including the main beam headlamp, so that when the main beamheadlamp is illuminated, the setting of the bridge network is altered.